title: Critical roles of interactions among switch I-preceding residues and between switch II and its neighboring alpha-helix in conformational dynamics of the GTP-bound Ras family small GTPases.
abstract: GTP-bound forms of Ras family small GTPases exhibit dynamic equilibrium between two interconverting conformations, "inactive" state 1 and "active" state 2. A great variation exists in their state distribution; H-Ras mainly adopts state 2, whereas M-Ras predominantly adopts state 1. Our previous studies based on comparison of crystal structures representing state 1 and state 2 revealed the importance of the hydrogen-bonding interactions of two flexible effector-interacting regions, switch I and switch II, with the γ-phosphate of GTP in establishing state 2 conformation. However, failure to obtain both state structures from a single protein hampered further analysis of state transition mechanisms. Here, we succeed in solving two crystal structures corresponding to state 1 and state 2 from a single Ras polypeptide, M-RasD41E, carrying an H-Ras-type substitution in residue 41, immediately preceding switch I, in complex with guanosine 5'-(β,γ-imido)triphosphate. Comparison among the two structures and other state 1 and state 2 structures of H-Ras/M-Ras reveal two new structural features playing critical roles in state dynamics; interaction of residues 31/41 (H-Ras/M-Ras) with residues 29/39 and 30/40, which induces a conformational change of switch I favoring its interaction with the γ-phosphate, and the hydrogen-bonding interaction of switch II with its neighboring α-helix, α3-helix, which induces a conformational change of switch II favoring its interaction with the γ-phosphate. The importance of the latter interaction is proved by mutational analyses of the residues involved in hydrogen bonding. These results define the two novel functional regions playing critical roles during state transition.
authors.affiliation: Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
authors.forename: Kousuke
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Fumi
authors.initials: F
authors.lastname: Shima
authors.forename: Shin
authors.initials: S
authors.lastname: Muraoka
authors.forename: Mitsugu
authors.initials: M
authors.lastname: Araki
authors.forename: Lizhi
authors.initials: L
authors.lastname: Hu
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ijiri
authors.forename: Rina
authors.initials: R
authors.lastname: Hirai
authors.forename: Jingling
authors.initials: J
authors.lastname: Liao
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshioka
authors.forename: Takashi
authors.initials: T
authors.lastname: Kumasaka
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Atsuo
authors.initials: A
authors.lastname: Tamura
authors.forename: Tohru
authors.initials: T
authors.lastname: Kataoka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D006801:Humans; D051379:Mice; D056004:Molecular Dynamics Simulation; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016283:Proto-Oncogene Proteins p21(ras) / Q000737:chemistry / Q000378:metabolism; D040681:Structural Homology, Protein; D018631:ras Proteins
chemical_list: C109418:Mras protein, mouse; C495971:Hras protein, mouse; D020559:Monomeric GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins